Chile and Argentina have evacuated a region near the Copahue volcano in the Andes on the border between the two countries, after fears intensified that it would erupt.

Both South American nations issued red alerts on Monday and put evacuation measures in place, with thousands leaving their homes.

Copahue is covered with glaciers and has around a dozen craters, one of which, “el Agrio” (the bitter one), has been spewing gas for months. The gases have diminished in the last few days but the seismic activity has increased – thousands of minor tremors have been registered in the last 48 hours – leading to the decision to evacuate.

“The situation is extremely complicated,” said Gonzalo Arroyo, regional director of ONEMI, the Chilean Home Office’s Emergency Office. “We’re talking about an up to 95 per cent chance of an eruption.”

Both countries have been quick to signal that the evacuation is a preventative measure. Chile’s President Sebastián Piñera called for calm when he announced on Monday that some 2,000 people located in a 15-mile radius of the volcano would have to leave.

This is not the first time that Copahue, towering at nearly 3,000m above sea level, has raised concerns. In December last year it began spewing ash that reached up to a mile in the sky, as well as lava.

There are some 3,000 volcanoes in the southern Andean mountain range, around 500 of them active. The last major Copahue eruption was in 1992.